ISOLATION, IDENTIFICATION AND CULTIVATION OF ENDOPHYTIC FUNGI FROM MEDICINAL PLANTS FOR THE PRODUCTION AND CHARACTERIZATION OF BIOACTIVE FUNGAL METABOLITES

Khan, Rizwana (2008) ISOLATION, IDENTIFICATION AND CULTIVATION OF ENDOPHYTIC FUNGI FROM MEDICINAL PLANTS FOR THE PRODUCTION AND CHARACTERIZATION OF BIOACTIVE FUNGAL METABOLITES. PhD thesis, University of Karachi, Karachi.

Abstract

Introduction: Endophytic fungi live inside the plant tissue without producing any symptom but provide protection to their host from insect, pest and herbivore, and the environmental stress conditions. The proposed research was initiated to investigate metabolic basis of parasitic endophytic fungi for their protective role on the host plant. The objective of this research work is to test a hypothesis that "endophytic fungi produce bioactive metabolite(s) which play an essential role to provide protection to their host against attack by other pathogens and environmental factors". The rational of the proposed work is that after it successful completion identification of novel bioactive metabolites could lead to the development of novel pharmaceutical agents against human diseases.
Methods: Endophytic fungal floras of two widely used medicinal plants (Withania somnifera and Calotropis procera) were used to perform the proposed studies. From Withania somnifera, a total of 643 segments (202 leaves, 391 stem and 50 root samples) from 20 different plants were screened, and from Calotropis procera, a total of 473 segments (118 leaf samples, and 355 stem samples) were screened from 9 plants. Some isolated endophytic fungi (not fully investigated for metabolites) were randomly selected for this study to identify their metabolites. The fungi used for detailed analysis of metabolites include: Alternaria alternata, Aspergillus auricomus, Chaetomium bostrychodes, Curvularia oryzae, Drechslera australiensis, Eurotium rub rum, MeZanospora fusispora, Myrothacium roridum and Penicillium sublaterium. Only Alternaria alternata was cultivated on large scale for production of metabolites, and detailed investigations were undertaken with respect to isolation, purification and structure elucidation of metabolites.
Results: Thirty-three endophytic fungi were isolated (24 different species) from Withania somnifera, and' nine endophytic fungi (8 species) were isolated from Calotropis procera. Almost all the endophytic fungal metabolites tested possess some degree of antifungal (antidermatophytic), antiprotozoal (antileishmanial) and phytotoxic activities. Many extracts also showed strong immunomodulatory activities.